1. Field of the Invention
The present invention relates to drawer type cooking devices having a turntable mechanism for heating an object to be cooked in a uniform manner.
The present invention also relates to drawer type cooking devices, wherein a drawer body with a door loading therein an object to be cooked is placed in the interior of the cooking device body and capable of being drawn out therefrom.
2. Description of the Related Art
In the prior art, cooking devices having a drawer body formed integrally with a door and capable of being drawn out to the front side of the cooking device have been proposed. Since this type of drawer type cooking devices can be built into the kitchen cabinet arranged downward of a countertop of a kitchen and installed without occupying the countertop area, it is suitably applied to a kitchen arrangement where multiple cooking devices are disposed spatially. Therefore, drawer type cooking devices have been considered as one type of cooking devices installed in a fitted kitchen or designed kitchen, and the use thereof is spreading especially in the United States.
FIG. 17 shows a perspective view of one example of a cabinet structure to which the cooking device is built in. There are two standard sizes for the width W of the mounting portion of the cabinet, which are 24 inches (approximately 62 cm) and 30 inches (approximately 76 cm). The height of the cabinet is 914 mm, the mounting surface height of the cooker is 483 mm, and the width, height and depth of the opening for loading the cooking device are 721 mm, 375 mm and 597 mm, respectively. The withstand load of the mounting surface is 160 kg or greater. A power supply outlet is disposed at a rear wall of the mounting opening portion. Since drawer type cooking devices have a common heating chamber width formed in the interior thereof and a common drawer body width, the drawer type cooking devices will correspond to the cabinet structure by changing or selecting the width of the door and the width of the outer casing.
The present applicant has proposed in patent document 1 (Japanese patent application laid-open publication No. 2005-221081=Publication of Japanese patent No. 4027325) a drawer type microwave oven as an example of a drawer type heating cooker, comprising a cooking device body having a heating chamber, a drawer body movably disposed within the cooking device body and capable of being drawn out of the heating chamber of the cooking device body, and slide rails for moving the drawer body within the cooking device body, wherein the slide rails are disposed outside the heating chamber, according to which the slide mechanisms can be formed without using components or materials having high heat resistance and flame resistance, and defective discharge via the microwaves can be prevented.
Since the prior art drawer type microwave oven disclosed in patent document 1 (Japanese patent application laid-open publication No. 2005-221081=Publication of Japanese patent No. 4027325) has slide mechanisms disposed on the side wall and the bottom wall of the heating chamber on the outer side of the heating chamber for moving the drawer body linearly, it is difficult to supply the microwaves generated via a high frequency generator through the side wall or the bottom wall of the heating chamber. Therefore, the arrangement adopts a ceiling power supply structure in which a waveguide for introducing microwaves is disposed on a ceiling portion of the body on the outer side of the heating chamber, and microwaves are supplied through the waveguide into the heating chamber.
On the other hand, general mass-produced microwave ovens to be placed on a kitchen counter-top include a turntable-type microwave oven in which a rotating turntable is disposed on the bottom side of the heating chamber as a uniform heating mechanism for heating an object to be heated such as food in a uniform manner, and a turntable having the object to be heated mounted thereon rotated during heating operation. Further, general mass-produced drawer type microwave ovens not capable of adopting turntables adopt a rotating stirrer or a rotating antenna-type microwave oven in which a rotating body having a nonuniform shape such as a metal plate is disposed within the microwave path on the ceiling portion, and the rotating body is rotated during heating operation so as to stir the microwave distribution within the heating chamber.
In order to adopt a turntable as a uniform heating mechanism in drawer type microwave ovens, a rotating turntable must be disposed on the drawer body. However, it is difficult to dispose a driving mechanism to a linearly-movable drawer body and to supply power thereto, and it is also difficult to arrange the turntable and the driving mechanism thereof within the vertically narrow space. Therefore, a rotating antenna as a uniform heating mechanism was arranged within the waveguide disposed on the ceiling surface of the heating chamber, which is a fixed area. In order to adopt this type of uniform heating mechanism, it was necessary to adopt a ceiling surface power supply structure for supplying microwaves through the ceiling into the heating chamber.
However, there have been strong demands from users favoring the traditional turntable structure for a drawer type microwave ovens adopting a turntable enabling to visually confirm the heating operation of the microwave oven. Further, according to a survey carried out by the present applicant to users of drawer type microwave ovens in the United States, it was discovered that many consumers desired the turntable mechanism to be adopted in microwave ovens.
On the other hand, according to another survey, it was discovered that there were strong demands for the ceiling height of the heating chamber of the drawer type microwave oven to be 180 mm or higher, so as to enable mugs of a famous coffee shop chain to be easily placed therein. Therefore, to set the ceiling height of the heating chamber to 180 mm or higher is a priority matter in designing the drawer type microwave oven.
As described, adopting turntables in drawer type microwave ovens has been a top priority technological challenge from the start of development of the drawer type microwave ovens, but it has not been possible for a long time.
One possible structure for adopting a turntable in a drawer type microwave oven is to first dispose a turntable on a bottom surface of the drawer body similar to the prior art microwave oven, and to dispose a rotary motor below the bottom surface of the drawer body as driving mechanism. According to such structure, the rotary motor moves together with the movement of the drawer body, so the mechanism does not require special engagement and disengagement operations.
However, since the area below the bottom surface of the drawer body is arranged within the heating chamber of the microwave oven into which microwaves are irradiated, it is impossible to dispose a rotary motor therein. Thus, it is impossible to dispose a turntable having the prior art structure to the drawer type microwave oven.
Further, since the power line connected to the rotary motor is moved and bent every time the drawer body is drawn out of or pushed into the heating chamber, it is extremely difficult to ensure the durability of the power line.
In order to solve the problems mentioned above, an engagement-disengagement mechanism must be adopted in which the driving unit requiring power supply such as the rotary motor is left in the main body and the turntable having food loaded thereon is moved together with the drawer body, wherein the driving unit and the turntable are engaged and disengaged by the movement of the drawer body.
One idea of such engagement-disengagement mechanism is a magnet coupling capable of transmitting power in a noncontact manner.
The present applicant has proposed (refer to patent document 3: Japanese patent application laid-open publication No. 2004-071213) a cooking device adopting a uniform heating mechanism for rotating a turntable via the drive force of a rotary motor disposed outside a casing by utilizing the magnetic coupling of a first magnet in the turntable and a second magnet in the drive mechanism in a general microwave oven. When the rotation mechanism proposed here is assembled in a drawer type cooking device, even without considering the cost of the magnet, there is a drawback in that a problem occurs in the operation of the drawer type cooking device.
That is, since the magnet coupling is linked magnetically in the perpendicular direction corresponding to the direction of the rotary shaft, the drive mechanism portion and the rotary operation portion are strongly attracted to each other in the perpendicular direction when the drawer body is to be opened, and a large load is applied to the movement mechanism moving in the direction orthogonal to the rotary shaft for moving the drawer body in the horizontal direction, according to which the drive force must be increased and smooth draw-out operation cannot be performed. Thus, from the viewpoint of cost and reliability, the magnet coupling could not be applied to drawer type microwave ovens.
Further, an engagement-disengagement mechanism for moving the turntable in the perpendicular direction is also considered as another example of the engagement-disengagement mechanism.
Such engagement-disengagement mechanism requires an anticollision means for the upward movement of the turntable when moving the receiver in the frontward direction. As a result, a limitation must be set to the height of the food and the like, and the ceiling height of the heating chamber is thus substantially lowered. Therefore, it is difficult to adopt an engagement-disengagement mechanism that moves the turntable in the perpendicular direction.
The present applicant has proposed in patent document 2 (Japanese utility model registration No. 2520881) a cooking device having a round turntable with a rotating body disposed near the circumference of the bottom surface of the turntable, a driven shaft fixed to the center portion of the bottom surface of the turntable passing through the receiver and having a driven gear fixed to the lower end thereof, the turntable rotatably mounted on the receiver, wherein the driven gear is engaged with a drive gear fixed to an end of the rotary shaft of the turntable driving motor when the door is closed, and the driven gear is disengaged from the drive gear when the door is opened and the receiver is moved in the frontward direction.
According to the cooking device, the drive gear and the driven gear are bevel gears that are widened toward opposite directions, and the gears are required be engaged when the door is closed in order to operate. In order for the gears to accurately encounter each other and to be accurately engaged with one another each time the door is repeatedly opened and closed, not only a very high component accuracy and assembly accuracy unprecedented in the prior art cooking device is required, but also the abrasion and deformation of the respective components caused by repeatedly opening and closing the door must be reduced significantly so as to maintain constant dimension and constant engagement. It is difficult to adopt such engagement-disengagement mechanism.
Even if one of the above-mentioned mechanisms is adopted, since the movement mechanism must be mounted on the outer side of the bottom portion of the heating chamber in order to support the weight of the door and the drawer body having food loaded therein according to the prior art drawer type microwave oven, the drive mechanism of the turntable cannot be extended downward from the heating chamber, and since microwaves are distributed also in the space between the drawer body and the heating chamber, it was difficult to dispose the motor composed of metallic components therein, so the installation of the drive mechanism became a problem.
As described, since adopting a turntable having an engagement-disengagement mechanism in the cooking device was a common challenge for those in the field of art, many studies have been performed related to various design options.
Further, U.S. Pat. No. 5,796,802 proposes a microwave oven having a division plate with multiple turn trays disposed within a heating chamber. This microwave oven has division plates mounting turn trays inserted horizontally in the heating chamber of the microwave oven, and the turn trays are attached removably to the division plate. A mechanism for rotating the turn trays adopts a rim (outer circumference) drive structure, having a gear disposed on a rotary shaft extending in the perpendicular direction of the drive motor disposed at the depth portion of the heating chamber, and the tray disposed on the division plate has a rotary teeth portion revolving at the lower rim portion of the tray, wherein the motor applies drive force to the rotary teeth portion to rotate the turn tray. If the division plate is attached to the depth portion of the heating chamber, the gear and the rotary teeth are mutually engaged, and the turn tray can be rotated via the motor. If the division plate is moved to the frontward direction, the gear and the rotary teeth are disengaged, so the turn tray will not be rotated. The rotary teeth portion has a relatively large radius so that a gentle cylindrical curved surface is formed, and it is tolerant to the positional dispersion with respect to the gear in the horizontal direction. Further, the gear and the rotary tooth portion can be engaged via friction transmission engagement instead of gear engagement.
However, as obvious to the engineers in this trade, turn trays for cooking devices of reasonable prices are almost without exception designed and manufactured for attaining lowest cost, not for high precisions. It is therefore deduced, according to this microwave oven, that the rotary teeth portion at a radial distance of approximately 15 cm from the center of rotation has a dimensional dispersion of a few mm from the center of rotation. Thus, when the turn tray is rotated, the rotary teeth portion and the gear repeatedly collide against one another generating noise and vibration, so it may be necessary to take measures to prevent separation for example by pressing the turn tray toward the depth direction via an elastic body. Moreover, if the turn tray is reduced in size due to the individual dimensional fluctuation of the turn tray, which often overwhelms manufacturer's control, there always are risks that the rotary teeth portion may not be engaged with the gear. However, the attempt to improve the dimensional precision of the turn tray in order to overcome this problem will result in the increase of cost.
Further, in order for the turn tray to be engaged to the gear in a disengageable manner, an opening must be formed to the engaged portion between the gear at the depth wall surface of the heating chamber and the rotary teeth portion. Thus, boiled over water or the like may flow downward through the opening. Drawer type cooking devices must have a space between the depth of the drawer body and the depth wall of the heating chamber for disposing the gear. Such arrangement is considered to create a drawback in that the depth of the drawer body is narrowed, by which the storage space for loading the object to be heated is also narrowed.
When drinks are to be heated in a drawer type microwave oven, drink containers are loaded in the drawer body drawn out of the heating chamber, but the heights thereof differ, and high narrow containers are intentionally formed by some designers. In order to store such high containers in the heating chamber, the height of the heating chamber must be increased, and if the microwave oven adopts a ceiling surface power supply structure, the ceiling height of the whole microwave oven body must necessarily be increased.
According to the prior art drawer type microwave ovens, power supply structures including the waveguide and uniform heating mechanisms such as a rotary antenna mechanism are disposed on the ceiling, and the ceiling must provide space for arranging such mechanisms. However, since the built-in space in which such drawer type microwave ovens are installed has a strict height limitation within the fitted kitchen or designed kitchen structure, it is actually impossible to increase the exterior height of the drawer type microwave ovens. Since the overall height of the microwave ovens was restricted, it was difficult to respond to the size-related demand of the object to be heated.
A cooking method using a thermal shock system in which high-temperature air heated via a heater is collided at high speed against an object to be cooked through an air blower is known. The present applicant proposes (refer to patent document 4: Publication of Japanese patent No. 3939232) a cooking device comprising a heating chamber for storing an object to be cooked, a heating means for heating the object to be cooked within the heating chamber, an air blower means for introducing hot air of the heating means into the heating chamber, and a control means for controlling the heating means and the air blower means, wherein the hot air via the heating means is blown into the heating chamber via multiple air blow paths and air supply outlets, and a control means controls the heating means and/or the air blower means and performs cooking via multiple circulating hot air systems by selecting and combining multiple air blow paths, thereby enabling a single cooking device to perform multiple cooking operations via selecting and combining the multiple air blow paths. Therefore, a single cooking device enables to perform multiple cooking methods, such as a cooking method preferable for high speed heating for cooking pizza or a lump of meat such as roast chicken, in which the heat transfer of the surface of the object to be cooked is improved by the wind pressure of the thermal shock, and a normal speed cooking method preferable for cooking an object to foam the same, such as baking a sponge cake, or for cooking an object containing much air.
It is difficult to introduce the hot air cooking function to the prior art drawer type microwave oven to obtain a composite cooking device. One reason for this is that the prior art drawer type microwave oven adopts a ceiling surface power supply structure, so that the uniform heating mechanism adopting a waveguide and a rotary antenna must be arranged on the outer space on the ceiling of the heating chamber, and attaching heat insulating materials required for hot air cooking is difficult. Another reason is that a high-speed hot air heating cooker suitably assembled as a high speed heating function to the microwave oven requires a uniform heating mechanism such as a turntable in which the object to be heated is moved within the heating chamber, so that it cannot easily be assembled to the prior art drawer type microwave oven adopting a rotary antenna instead of a turntable.
Moreover, the cooker with a high speed hot air cooking device proposed in patent document 4 (publication of Japanese patent No. 3939232) assumes a consumption power exceeding 2000 W since the specification thereof realizes a high speed cooking operation corresponding to or exceeding the cooking operation using a gas oven, and has a large-capacity heating chamber. Therefore, in order to adopt the high-speed hot air cooking function in a drawer type cooking device built into a kitchen and assuming a consumption power of approximately 1200 W, it is necessary to reduce the consumption power and improve the heat radiation performance.